// seedrandom.js version 2.3.4
// Author: David Bau
// Date: 2014 Mar 9
//
// Defines a method Math.seedrandom() that, when called, substitutes
// an explicitly seeded RC4-based algorithm for Math.random().  Also
// supports automatic seeding from local or network sources of entropy.
// Can be used as a node.js or AMD module.  Can be called with "new"
// to create a local PRNG without changing Math.random.
//
// Basic usage:
//
//   <script src=http://davidbau.com/encode/seedrandom.min.js></script>
//
//   Math.seedrandom('yay.');  // Sets Math.random to a function that is
//                             // initialized using the given explicit seed.
//
//   Math.seedrandom();        // Sets Math.random to a function that is
//                             // seeded using the current time, dom state,
//                             // and other accumulated local entropy.
//                             // The generated seed string is returned.
//
//   Math.seedrandom('yowza.', true);
//                             // Seeds using the given explicit seed mixed
//                             // together with accumulated entropy.
//
//   <script src="https://jsonlib.appspot.com/urandom?callback=Math.seedrandom">
//   </script>                 <!-- Seeds using urandom bits from a server. -->
//
//   Math.seedrandom("hello.");           // Behavior is the same everywhere:
//   document.write(Math.random());       // Always 0.9282578795792454
//   document.write(Math.random());       // Always 0.3752569768646784
//
// Math.seedrandom can be used as a constructor to return a seeded PRNG
// that is independent of Math.random:
//
//   var myrng = new Math.seedrandom('yay.');
//   var n = myrng();          // Using "new" creates a local prng without
//                             // altering Math.random.
//
// When used as a module, seedrandom is a function that returns a seeded
// PRNG instance without altering Math.random:
//
//   // With node.js (after "npm install seedrandom"):
//   var seedrandom = require('seedrandom');
//   var rng = seedrandom('hello.');
//   console.log(rng());                  // always 0.9282578795792454
//
//   // With require.js or other AMD loader:
//   require(['seedrandom'], function(seedrandom) {
//     var rng = seedrandom('hello.');
//     console.log(rng());                // always 0.9282578795792454
//   });
//
// More examples:
//
//   var seed = Math.seedrandom();        // Use prng with an automatic seed.
//   document.write(Math.random());       // Pretty much unpredictable x.
//
//   var rng = new Math.seedrandom(seed); // A new prng with the same seed.
//   document.write(rng());               // Repeat the 'unpredictable' x.
//
//   function reseed(event, count) {      // Define a custom entropy collector.
//     var t = [];
//     function w(e) {
//       t.push([e.pageX, e.pageY, +new Date]);
//       if (t.length < count) { return; }
//       document.removeEventListener(event, w);
//       Math.seedrandom(t, true);        // Mix in any previous entropy.
//     }
//     document.addEventListener(event, w);
//   }
//   reseed('mousemove', 100);            // Reseed after 100 mouse moves.
//
// The callback third arg can be used to get both the prng and the seed.
// The following returns both an autoseeded prng and the seed as an object,
// without mutating Math.random:
//
//   var obj = Math.seedrandom(null, false, function(prng, seed) {
//     return { random: prng, seed: seed };
//   });
//
// Version notes:
//
// The random number sequence is the same as version 1.0 for string seeds.
// * Version 2.0 changed the sequence for non-string seeds.
// * Version 2.1 speeds seeding and uses window.crypto to autoseed if present.
// * Version 2.2 alters non-crypto autoseeding to sweep up entropy from plugins.
// * Version 2.3 adds support for "new", module loading, and a null seed arg.
// * Version 2.3.1 adds a build environment, module packaging, and tests.
// * Version 2.3.3 fixes bugs on IE8, and switches to MIT license.
// * Version 2.3.4 fixes documentation to contain the MIT license.
//
// The standard ARC4 key scheduler cycles short keys, which means that
// seedrandom('ab') is equivalent to seedrandom('abab') and 'ababab'.
// Therefore it is a good idea to add a terminator to avoid trivial
// equivalences on short string seeds, e.g., Math.seedrandom(str + '\0').
// Starting with version 2.0, a terminator is added automatically for
// non-string seeds, so seeding with the number 111 is the same as seeding
// with '111\0'.
//
// When seedrandom() is called with zero args or a null seed, it uses a
// seed drawn from the browser crypto object if present.  If there is no
// crypto support, seedrandom() uses the current time, the native rng,
// and a walk of several DOM objects to collect a few bits of entropy.
//
// Each time the one- or two-argument forms of seedrandom are called,
// entropy from the passed seed is accumulated in a pool to help generate
// future seeds for the zero- and two-argument forms of seedrandom.
//
// On speed - This javascript implementation of Math.random() is several
// times slower than the built-in Math.random() because it is not native
// code, but that is typically fast enough.  Some details (timings on
// Chrome 25 on a 2010 vintage macbook):
//
// seeded Math.random()          - avg less than 0.0002 milliseconds per call
// seedrandom('explicit.')       - avg less than 0.2 milliseconds per call
// seedrandom('explicit.', true) - avg less than 0.2 milliseconds per call
// seedrandom() with crypto      - avg less than 0.2 milliseconds per call
//
// Autoseeding without crypto is somewhat slower, about 20-30 milliseconds on
// a 2012 windows 7 1.5ghz i5 laptop, as seen on Firefox 19, IE 10, and Opera.
// Seeded rng calls themselves are fast across these browsers, with slowest
// numbers on Opera at about 0.0005 ms per seeded Math.random().
//
// LICENSE (MIT):
//
// Copyright (c)2014 David Bau.
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

/**
 * All code is in an anonymous closure to keep the global namespace clean.
 */
(function (
    global, pool, math, width, chunks, digits, module, define, rngname) {

//
// The following constants are related to IEEE 754 limits.
//
    var startdenom = math.pow(width, chunks),
        significance = math.pow(2, digits),
        overflow = significance * 2,
        mask = width - 1,

//
// seedrandom()
// This is the seedrandom function described above.
//
        impl = math['seed' + rngname] = function(seed, use_entropy, callback) {
            var key = [];

            // Flatten the seed string or build one from local entropy if needed.
            var shortseed = mixkey(flatten(
                use_entropy ? [seed, tostring(pool)] :
                    (seed == null) ? autoseed() : seed, 3), key);

            // Use the seed to initialize an ARC4 generator.
            var arc4 = new ARC4(key);

            // Mix the randomness into accumulated entropy.
            mixkey(tostring(arc4.S), pool);

            // Calling convention: what to return as a function of prng, seed, is_math.
            return (callback ||
                // If called as a method of Math (Math.seedrandom()), mutate Math.random
                // because that is how seedrandom.js has worked since v1.0.  Otherwise,
                // it is a newer calling convention, so return the prng directly.
                function(prng, seed, is_math_call) {
                    if (is_math_call) { math[rngname] = prng; return seed; }
                    else return prng;
                })(

                // This function returns a random double in [0, 1) that contains
                // randomness in every bit of the mantissa of the IEEE 754 value.
                function() {
                    var n = arc4.g(chunks),             // Start with a numerator n < 2 ^ 48
                        d = startdenom,                 //   and denominator d = 2 ^ 48.
                        x = 0;                          //   and no 'extra last byte'.
                    while (n < significance) {          // Fill up all significant digits by
                        n = (n + x) * width;              //   shifting numerator and
                        d *= width;                       //   denominator and generating a
                        x = arc4.g(1);                    //   new least-significant-byte.
                    }
                    while (n >= overflow) {             // To avoid rounding up, before adding
                        n /= 2;                           //   last byte, shift everything
                        d /= 2;                           //   right using integer math until
                        x >>>= 1;                         //   we have exactly the desired bits.
                    }
                    return (n + x) / d;                 // Form the number within [0, 1).
                }, shortseed, this == math);
        };

//
// ARC4
//
// An ARC4 implementation.  The constructor takes a key in the form of
// an array of at most (width) integers that should be 0 <= x < (width).
//
// The g(count) method returns a pseudorandom integer that concatenates
// the next (count) outputs from ARC4.  Its return value is a number x
// that is in the range 0 <= x < (width ^ count).
//
    /** @constructor */
    function ARC4(key) {
        var t, keylen = key.length,
            me = this, i = 0, j = me.i = me.j = 0, s = me.S = [];

        // The empty key [] is treated as [0].
        if (!keylen) { key = [keylen++]; }

        // Set up S using the standard key scheduling algorithm.
        while (i < width) {
            s[i] = i++;
        }
        for (i = 0; i < width; i++) {
            s[i] = s[j = mask & (j + key[i % keylen] + (t = s[i]))];
            s[j] = t;
        }

        // The "g" method returns the next (count) outputs as one number.
        (me.g = function(count) {
            // Using instance members instead of closure state nearly doubles speed.
            var t, r = 0,
                i = me.i, j = me.j, s = me.S;
            while (count--) {
                t = s[i = mask & (i + 1)];
                r = r * width + s[mask & ((s[i] = s[j = mask & (j + t)]) + (s[j] = t))];
            }
            me.i = i; me.j = j;
            return r;
            // For robust unpredictability discard an initial batch of values.
            // See http://www.rsa.com/rsalabs/node.asp?id=2009
        })(width);
    }

//
// flatten()
// Converts an object tree to nested arrays of strings.
//
    function flatten(obj, depth) {
        var result = [], typ = (typeof obj), prop;
        if (depth && typ == 'object') {
            for (prop in obj) {
                try { result.push(flatten(obj[prop], depth - 1)); } catch (e) {}
            }
        }
        return (result.length ? result : typ == 'string' ? obj : obj + '\0');
    }

//
// mixkey()
// Mixes a string seed into a key that is an array of integers, and
// returns a shortened string seed that is equivalent to the result key.
//
    function mixkey(seed, key) {
        var stringseed = seed + '', smear, j = 0;
        while (j < stringseed.length) {
            key[mask & j] =
                mask & ((smear ^= key[mask & j] * 19) + stringseed.charCodeAt(j++));
        }
        return tostring(key);
    }

//
// autoseed()
// Returns an object for autoseeding, using window.crypto if available.
//
    /** @param {Uint8Array|Navigator=} seed */
    function autoseed(seed) {
        try {
            global.crypto.getRandomValues(seed = new Uint8Array(width));
            return tostring(seed);
        } catch (e) {
            return [+new Date, global, (seed = global.navigator) && seed.plugins,
                global.screen, tostring(pool)];
        }
    }

//
// tostring()
// Converts an array of charcodes to a string
//
    function tostring(a) {
        return String.fromCharCode.apply(0, a);
    }

//
// When seedrandom.js is loaded, we immediately mix a few bits
// from the built-in RNG into the entropy pool.  Because we do
// not want to intefere with determinstic PRNG state later,
// seedrandom will not call math.random on its own again after
// initialization.
//
    mixkey(math[rngname](), pool);

//
// Nodejs and AMD support: export the implemenation as a module using
// either convention.
//
    if (module && module.exports) {
        module.exports = impl;
    } else if (define && define.amd) {
        define(function() { return impl; });
    }

// End anonymous scope, and pass initial values.
})(
        this,   // global window object
        [],     // pool: entropy pool starts empty
        Math,   // math: package containing random, pow, and seedrandom
        256,    // width: each RC4 output is 0 <= x < 256
        6,      // chunks: at least six RC4 outputs for each double
        52,     // digits: there are 52 significant digits in a double
        (typeof module) == 'object' && module,    // present in node.js
        (typeof define) == 'function' && define,  // present with an AMD loader
        'random'// rngname: name for Math.random and Math.seedrandom
    );
